A standard motor-vehicle door latch has a latch housing mounted on a door edge, a latch fork pivotal on the housing and latchingly engageable around a latch element mounted on the doorpost or body frame, and a latch pawl mounted on the housing for retaining the fork around the element or releasing it to free the element. This pawl can be moved into the fork-freeing position by inside and outside door handles, and the outside handle at least can be decoupled from the pawl by locking mechanisms inside and outside the door.
The latch element can be a bolt, wedge, or the like and a bumper is frequently provided on the fork or latch element so that the latch element can overtravel somewhat when the door, which can be a hood or trunk lid, is closed, leaving the bumper compressed in the latch mechanism to hold everything tight against rattling.
The overtravel of the door on closing is necessary in order to ensure that it remains tightly closed and to allow the pawl to swing into position. The bumper typically serves to allow the door to spring back somewhat and often works with or is in fact formed at least partially by elastomeric seals provided around the rim of the door so as to provide, in effect, an elastomeric seat in which the door sits when closed. The exact position of the door when closed, however, is typically established in the latch by an abutment which has some degree of adjustability so that the closed position can be set exactly.
Nonetheless the considerable mass of the door, the dynamic and changing forces it is subjected to, and other factors lead to a less than perfect seating and corresponding rattling with time. When the bumper and door seal are insufficiently compressed the door is certain to rattle, and when excessively compressed it may be difficult to latch the door, or unwanted metal-to-metal contact can be created for another noise problem.